Optical information recording medium

Abstract

An optical information recording medium which can be played back by both a playback system for an SD (Super-density Disk) and a playback system for an HDMCD (High Density Multimedia Compact Disk), or by both the playback system for the SD and a playback system for a CD (Compact Disk). The optical information recording medium comprises a first transparent substrate which includes a smooth surface, and a first information surface bearing pits correspondent to first recorded information, the first information surface being covered with a semitransparent film which transmits part of a playback beam and reflects part thereof; and a second transparent substrate which includes a smooth surface, and a second information surface bearing pits correspondent to second recorded information, the second information surface being covered with a reflective film which reflects the greater part of the playback beam; the second transparent substrate being stacked on the first transparent substrate with the first information surface of the latter overlaid by the smooth surface of the former.

What is claimed is: 
     
       1. An optical information recording medium comprising: a first transparent substrate including a first smooth surface and a first information surface;   a first partially reflective film formed on said first information surface which reflects a portion of a first playback beam having a first wavelength and transmits a portion of a second playback beam having a second wavelength;   a second transparent substrate including a second smooth surface and a second information surface; and   a second reflective film formed on said second information surface which reflects a second playback beam having a second wavelength;   wherein said second transparent substrate is stacked on said first transparent substrate so that said second smooth surface faces said first information surface such that   a first information recorded on said first information surface is reproduced by said first playback beam transmitted through said first transparent substrate and second information recorded on said second information surface has a different recording format than said first information surface and is reproduced by said second playback beam transmitted through said first transparent substrate and said second transparent substrate.   
     
     
       2. The optical information recording medium of claim 1, wherein said first transparent substrate and said second transparent substrate are each 0.6 (mm) in thickness. 
     
     
       3. The optical information recording medium of claim 1, wherein said information recorded on said first information surface conforms to a digital video disk specification; and said information recorded on said second information surface conforms to the Compact Disk specification. 
     
     
       4. The optical information recording medium of claim 1, wherein said first information recorded on said first information surface conforms to a data compression method in accordance with Moving Picture Experts Group 2 (MPEG 2); and   said second information recorded on said second information surface conforms to a data compression method in accordance with Moving Picture Experts Group 1 (MPEG 1).   
     
     
       5. The optical information recording medium of claim 1, wherein the recording density of said first information is higher than the recording density of said second information. 
     
     
       6. The optical information recording medium of claim 1 wherein the first wavelength is 650-680 nanometers and the second wavelength is 780 nanometers.